incrsum

Compute a sum incrementally.

The sum is defined as

Usage

var incrsum = require( '@stdlib/stats/incr/sum' );

incrsum()

Returns an accumulator function which incrementally computes a sum.

var accumulator = incrsum();

accumulator( [x] )

If provided an input value x, the accumulator function returns an updated sum. If not provided an input value x, the accumulator function returns the current sum.

var accumulator = incrsum();

var sum = accumulator( 2.0 );
// returns 2.0

sum = accumulator( 1.0 );
// returns 3.0

sum = accumulator( 3.0 );
// returns 6.0

sum = accumulator();
// returns 6.0

Notes

Input values are not type checked. If provided NaN or a value which, when used in computations, results in NaN, the accumulated value is NaN for all future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly before passing the value to the accumulator function.
For long running accumulations or accumulations of large numbers, care should be taken to prevent overflow.

Examples

var randu = require( '@stdlib/random/base/randu' );
var incrsum = require( '@stdlib/stats/incr/sum' );

var accumulator;
var v;
var i;

// Initialize an accumulator:
accumulator = incrsum();

// For each simulated datum, update the sum...
for ( i = 0; i < 100; i++ ) {
    v = randu() * 100.0;
    accumulator( v );
}
console.log( accumulator() );

References

Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." Computing 76 (3): 279–93. doi:10.1007/s00607-005-0139-x.